Wooden structural elements can be fastened together by driven fasteners such as common nails. Nails have a head and a shank. The head provides an impact surface onto which a force is applied to drive the fastener. The shank typically includes a pointed end opposite the head. The pointed end pierces the wooden structural elements, thus diminishing the force required to drive the nail into the structural element.
Nails are typically used to fasten an outer structural element to an inner structural element. The fastening of an outer and inner wooden structural elements is complete when the head is flush with the outer structural element and the shank has been driven entirely through the outer structural element into the inner structural element.
One specific use of nails is the securement of structural elements such as panelized structural sheathing (plywood, oriented strand board (OSB), etc.) to inner structural framing elements (e.g., joists, 2xc3x974""s, and roof rafters). Structural sheathing, as defined by the 1999 APA Panel Handbook and Grade Glossary, which is incorporated herein by reference, is the xe2x80x9cstructural covering, usually of wood panels or boards, on the outside surfaces of framing. It provides support for construction, snow and wind loads and backing for attaching exterior facing materials such as wall siding, roof shingles or underlayment in double layer floors.xe2x80x9d
Structural sheathing is typically vulnerable to uplift in a high wind event such as a tornado or hurricane. Structural sheathing is also vulnerable to earthquake loads where large deflections of structural elements, to which the sheathing is secured, may occur. In highly stressed situations, of which high winds and earthquakes are but two examples, retention of the sheathing is necessary to minimize property damage.
There are three types of loading conditions that can occur to cause a nail to fail: an axial force (a load parallel to the nail shank), a shear force (a load perpendicular to the nail shank), and a combination of these two loading conditions. In a situation where a nail is axially loaded the nail can typically fail in one of two modes. A first failure mode is a withdrawal failure. A withdrawal failure occurs when the nail shank withdraws from the inner structural element allowing the outer structural element to separate from the inner structural element. A second failure mode is known as a xe2x80x9cpull throughxe2x80x9d failure. A pull through failure occurs when the nail head is pulled through the outer structural element allowing the outer structural element to separate from the inner structural element. In a situation where the nail is loaded in a shear condition, there are numerous failure modes that can occur: withdrawal, pull through, wood crushing, and nail shank bending. ASTM F1667-95 is the standard specification that covers driven fasteners including common nails. Head sizes for nails such as common nails are specified within this standard. Head size has typically been set for nails such as common nails based on the shank diameter and shank length.
ASTM F1667-95 includes a Table 16, which is the standard specification for nails for use mechanical drivers. The nails listed in this table are denoted as common nails. The nails listed in this table have a length and a shank diameter. However, nail head sizes are not listed in this specification. In Table 15 of the ASTM F1667-95 Standard Specification, the head sizes for common nails which are not mechanically driven are provided. Additionally, it should be noted that nails other than those listed in Table 16 (i.e., Tables 3-15 and 17-55) are typically not specifically specified for use with mechanical drivers and would typically be sold in bulk. However, some of the these other nails are available in a packaged form for use with a mechanical driver.
Head sizes for nails mechanically driven are typically smaller than those which are not mechanically driven (i.e., manually driven). Smaller head sizes are needed for mechanically driven nails because mechanically driven nails are sold more typically in a packaged collated form and there is often a requirement that the nail package be as dense as possible. In particular, packaged nails sold in a stick form typically require a minimum of spacing separating the nail shanks of adjacent nails. For this reason, large head sizes have typically not been used for nails sold in a packaged form. Additionally, small nail head sizes have been used for mechanically driven nails, because larger nail head sizes have been considered detrimental to easily passing through the mechanical driver. Consequently, smaller head sizes have been used for nails which are sold in package form to be driven by mechanical drivers than would be used for manually driven nails sold in bulk. Mechanical drivers also typically have a maximum nail head size that is usable with the mechanism.
NER-272 is the document that governs the design capacities allowed for power driver nails in wood framed construction. Additionally, it is the document that allows the power driven fastener to be utilized in lieu of a hand driven fastener in the major building codes (BOCA, ICBO, and SBCCI). The tables in NER-272 (5-22 and 28-37) specify the nail diameter, length and spacing for use in the attachment of structural sheathing to a framing member for a floor, wall or roof. The nails specified for these structural applications have a length between 1⅝ and 3 inches with a diameter between 0.092 and 0.148 in. Basically, it can be determined that a conventionally acceptable nail for sheathing is:
1. Manufactured from a form of steel wire;
2. Has a single round shank;
3. Has a shank diameter between 0.092 and 0.148 in.; and
4. Has a length between 1⅝ and 3 inches.
In addition to the four criteria listed above, it is also recognized that nails suitable for sheathing preferably have surface deformations, which are typically ring barbs, to provide a resistance to pull out.
There exists a need for a nail that is more cost effective than existing nails that achieve the desired functional characteristics for sheathing nails. There particularly exists a need for such sheathing nails that can be used for high uplift applications, such as roof sheathing.
There is also a need for, in combination, a wooden structural sheathing panel, a framing structure, and a series of nails that is more cost effective than existing structures.
The nail of the present invention is preferably manufactured from steel wire. The nail comprises a round head having a flat top surface suitable for being driven into a flush relationship with an exterior surface of a sheathing panel and a bottom surface. A single elongate shank that is integral with the head extends from the head bottom surface. The elongate shank further includes a point opposite the head and a plurality of surface deformations disposed on the shank. The surface deformations are configured to provide an enhanced resistance to panel separation by withdrawal of the nail shank from a framing structure. The shank has a substantially round cross-section having a shank diameter between 0.092 and 0.148 in. The nail further has a length defining the distance from the head to the shank point of between 1.625 inches and 3.00 inches. The head diameter provides an enlarged bottom head surface area for engaging the exterior surface of a sheathing panel to enhance resistance to panel separation by head pull through. The ratio of the head diameter to shank diameter is between 2.70 and 3.37.
The present invention also comprises a structure having a wooden structural sheathing panel secured to a framing structure through a plurality of the nails of the present invention. The present further comprises a method of fastening a wooden structural sheathing panel to a framing structure using a plurality of nails of the present invention. The present invention still further comprises a package of collated nails of the present invention.
An outer structural element is secured to an inner structural element through the use of the nail of the present invention. The nail of the present invention has particular benefits in applications such as the securement of outer structural elements such as panelized structural sheathing (plywood, orientated strand board (OSB), etc.) to inner structural framing elements such as joists, 2xc3x974""s, and roof rafters, which are typically used in framing structures.
The enlarged head provides a first clamping surface that is seated against an exterior surface of the sheathing panel into which the nail is first driven. The framing structure within which the deformed shank is disposed, is the second clamping surface. Through the provision of an enlarged head and a deformed shank, the ability of the nail to maintain the securement of the sheathing panel to the framing structure is enhanced. The nail of the present invention provides a nail head clamping surface of the necessary size to clamp a sheathing panel between the nail head and a framing structure, within which the deformed shank is disposed.
The shank of the present invention nail includes surface deformations such as rings to resist withdrawal. Accordingly, the deformed shank increases the force required to withdraw the nail shank from the framing structure (i.e. the withdrawal capacity).
The enlarged head of the present invention nail increases the surface area in contact with the exterior surface of a sheathing panel. The enlarged surface area subsequently ensures that a larger area of the sheathing panel would have to be pulled though the nail head for a pull through failure to occur. Accordingly, the pull through capacity of the sheathing panel is correspondingly increased through the use of the nail of the present invention.
The pull through capacity of a sheathing panel may be determined experimentally. The withdrawal capacity of the nail shank may also be determined experimentally. Accordingly, the nails of the present invention may be designed such the withdrawal capacity exceeds the pull through capacity.
One embodiment of a nail manufactured in accordance with the present invention has been shown in experiments to provide up to a 20-97 percent increase in panel uplift capacity as compared to 8d common nails with similar nail spacing. Additionally, the nail of the present invention has been shown in experiments to provide a 14 percent increase in shear capacity and similar energy dissipation as compared to 8d common nails. The enlarged nail head has been shown in experiments to provide a 10 percent increase in pull through capacity as compared to 8d common nails.
The nail of the present invention also has particular benefits in applications such as the securement of outer structural elements such as structural sheathing used in sub-flooring to floor joists or other load bearing structural elements in the sub-flooring. If the nails used to secure the sheathing to the sub-flooring loosen, the floor will squeak. Squeaking floors present a nuisance and source of irritation for home dwellers where this phenomenon occurs. The nail of the present invention provides a clamping force on the sub-floor sheathing. This clamping force minimizes the possibility that nails used to fasten the sub-floor sheathing will loosen and that floors secured by the nails will be less likely to squeak.
Other advantages of the nail of the present invention are also derived from the enlarged diameter nail head. Nails should be driven until the nail head is flush with exterior surface of the sheathing. If the nail is power driven, there is an opportunity to drive a nail beyond the flush position, to a position beneath the exterior surface of the sheathing. The nail head compresses and damages the cellular structure of the sheathing as it is driven past the flush position. The strength of the sheathing is correspondingly lowered as a result of an over driven nail. The enlarged head of the nail of the present invention provides a large surface area that is more easily driven to a position where the head is contacting the exterior surface of the sheathing and is substantially flush with the sheathing surface. The large surface area of the enlarged nail head distributes the driving impact forces over a greater area, thus minimizing the possibility that the nail can be over driven. And, as the structural damage caused by overdriving the nail head is less likely to occur through the use of the nail of the present invention, pull through failures are correspondingly decreased.
These and other aspects and advantages of the invention can be realized by the embodiments of the nail of the invention. Other objects, aspects, and advantages of the embodiments of the invention will become apparent from the detailed description taken in conjunction with the drawings.